A NEW SPECIES OF THE WOMBAT WARENDJA FROM LATE MIOCENE DEPOSITS AT RIVERSLEIGH, NORTH-WEST QUEENSLAND, AUSTRALIA

Abstract:  A new species of the plesiomorphic wombat Warendja is described. Warendja encorensis sp. nov., the second species to be attributed to this genus, is known from a single fossil locality (Encore Site) at Riversleigh, north-west Queensland. Specimens of W. encorensis are limited to isolated teeth, two mandibular fragments and a maxillary fragment. Two molars preserve the unworn crown morphology. Encore Site has been estimated to be late Miocene in age, making these the only known specimens of Warendja to be clearly older than Pleistocene. Warendja encorensis is also the first described species of wombat from Miocene deposits to which hypselodont teeth have been attributed. It differs from W. wakefieldi in its larger size, distribution of enamel, and in details of the incisor and premolar morphology.     

Sticky bivalves from the Mesozoic: clues to the origin of the anomalodesmatan arenophilic system

Arenophilic glands represent the only molluscan example of multicellular organs solely concerned with adhesion of foreign particles to the external surfaces of an organism. The glands are exclusive to the bivalve clade Anomalodesmata, but do not occur in all component taxa, having been declared absent in a number of families, including Pholadomyidae. This paper records and describes for the first time the arenophilic apparatus of Pholadomya candida G. B. Sowerby I, 1823, and demonstrates that secretion from these glands is at times preserved in the fossil record. In P. candida , arenophilic glands in the middle mantle folds discharge their products on top of the shell as the animal grows, forming radial lines of secretion that comprise a meandering main strand and numerous thin threads projecting in tufts. The arrangement is similar to that of other families, corroborating the hypothesis that the glands are a synapomorphy of crown-group anomalodesmatans. Instances of preserved secretion in fossil Pholadomya , ranging in age almost to the initial appearance of the genus in the Late Triassic, suggest that fossilized arenophilic secretion may aid systematic studies of problematic fossil groups traditionally included in Anomalodesmata.     

Effects of shoreline development on the nearshore environment in large deep oligotrophic lakes

1. In large deep oligotrophic lakes, the shallow nearshore waters may provide the most important habitat for animals to feed and breed, and it is this area of the lake where humans are most likely to have initial impacts as the shoreline is developed. Nutrients in fertilizers, sediments and sewage effluents are likely to be rapidly intercepted by nearshore algae at the lake edge, having heterogeneous effects nearshore before offshore effects are noted. 2. Here we examined the spatially explicit effects of residential development on nearshore periphyton communities in three large deep oligotrophic lakes that have all experienced modest residential development in the Pacific Northwest of the United States. We demonstrate that substantial nearshore changes in the basal food web are detectable even with low levels of shoreline development. These changes can potentially affect whole‐lake food web dynamics. 3. For our primary study site (Lake Crescent, Washington, USA), we found that algal biomass and accumulation of detritus were higher at developed sites. In addition, both macroinvertebrate and periphyton communities exhibited a shift in composition with more detritivores and filamentous green algae at developed sites. These differences were more pronounced during the spring than at other times of year. 4. A complementary investigation of field patterns in Priest Lake and Lake Pend Oreille (Idaho, USA) suggested that, although spatial and temporal patterns were idiosyncratic, indicators of productivity and the presence of filamentous green algae were generally higher at developed sites across lakes. 5. Stable isotope signatures and water column nutrients were not useful in distinguishing developed and undeveloped sites, increasing the potential usefulness of periphyton monitoring during early stages of lake development. 6. A laboratory investigation suggested that common macroinvertebrate grazers assimilated a much greater proportion of diatoms than the filamentous green algae that are associated with fertilization at developed sites. 7. These findings have at least two clear implications: (i) periphyton may be used to detect human impacts before disturbance is evident in offshore monitoring programmes and (ii) nearshore impacts in response to modest residential development have the potential to disrupt lake food web dynamics.     

Modelling stress in the feeding apparatus of seahorses and pipefishes (Teleostei: Syngnathidae)

Seahorses and pipefishes are extremely fast suction feeders, and the fast strikes probably result in large and rapid pressure drops in the buccal cavity. These rapid drops in pressure imply heavy mechanical loading on the cranium; hence, the feeding apparatus is thought to experience high levels of stress. We used finite element analysis (FEA) to investigate where stress accumulates under strong suction pressure, and whether there is a difference in craniofacial stress distribution between long‐ and short‐snouted species. The expectation was that high stress levels would occur at the articulations and in the cartilaginous regions of the cranium, and that, given the same pressure, the skulls of long‐snouted species would exhibit lower stress levels than the skulls of short‐snouted species, as an evolutionary increase in snout length might have made these species structurally better adapted to deal with high suction pressures. The results partially support the first hypothesis: except for Dunckerocampus dactyliophorus, all models show peak stress concentrations at the articulations and cartilaginous regions. However, no simple relationship between snout length and the magnitudes of stress predicted by the FEA was found. In an attempt to explain this lack of a relationship, the methodology was evaluated by assessing the effect of hyoid position and model construction on the stress distribution. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 680–691.     

Non‐consumptive effects of a natural enemy on a non‐prey herbivore population

1. Predator–prey interactions have traditionally focused on the consumptive effects that predators have on prey. However, predators can also reduce the abundance of prey through behaviourally‐mediated non‐consumptive effects. For example, pea aphids (Acyrthosiphon pisum Harris) drop from their host plants in response to the risk of attack, reducing population sizes as a consequence of lost feeding opportunities. 2. The objective of the present study was to determine whether the non‐consumptive effects of predators could extend to non‐prey herbivore populations as a result of non‐lethal incidental interactions between herbivores and foraging natural enemies. 3. Polyculture habitats consisting of green peach aphids (Myzus persicae Sulzer) feeding on collards and pea aphids feeding on fava beans were established in greenhouse cages. Aphidius colemani Viereck, a generalist parasitoid that attacks green peach aphids but not pea aphids, was released into half of the cages and the abundance of the non‐host pea aphid was assessed. 4. Parasitoids reduced the population growth of the non‐host pea aphid by increasing the frequency of defensive drops; but this effect was dependent on the presence of green peach aphids. 5. Parasitoids probably elicited the pea aphid dropping behaviour through physical contact with pea aphids while foraging for green peach aphids. It is unlikely that pea aphids were responding to volatile alarm chemicals emitted by green peach aphids in the presence of the parasitoid. 6. In conclusion, the escape response of the pea aphid provided the opportunity for a parasitoid to have non‐target effects on an herbivore with which it did not engage in a trophic interaction. The implication is that natural enemies with narrow diet breadths have the potential to influence the abundance of a broad range of prey and non‐prey species via non‐consumptive effects.     

Genetic variability in Irish populations of the invasive zebra mussel, Dreissena polymorpha: discordant estimates of population differentiation from allozymes and microsatellites

1. The recent arrival and explosive spread of the zebra mussel, Dreissena polymorpha (Pallas), in Ireland provided a rare opportunity to study the population genetics of an invasive species.
2. Eight polymorphic allozyme loci ( ACO-1, ACO-2 , EST-D, GPI, IDH-2, MDH, OPDH and PGM ) were used to investigate genetic diversity and population structure in five Irish populations, and the results were compared with those from a previous microsatellite study on the same samples.
3. The mean number of alleles per locus (2.7 ± 0.1) was similar to the mean for the same loci in European populations, suggesting that Irish founder populations were large and/or multiple colonization events took place after foundation. A deficiency of heterozygotes was observed in all populations, but was uneven across loci.
4. Pairwise comparisons, using Fisher's exact tests and F _ST values, revealed significant genetic differentiation among populations. The overall multilocus F _ST estimate was 0.118 ± 0.045, which contrasted with an estimate of 0.015 ± 0.007 from five microsatellite loci on the same samples in a previous study.
5. Assuming that microsatellites can be used as a neutral baseline, the discordant results from allozymes and microsatellites suggest that selection may be acting on some allozyme loci, specifically ACO-1, ACO-2 , IDH-2 and MDH, which contributed most to the significant differentiation between samples.     

Experimental and Analytical Studies of Pteridophytes: XXX. Further Investigations of the Formation of Buds and Leaves in Dryopteris aristata Druce

The influence of the shoot apex upon leaf and bud formationin the fern Dryopteris aristata has been investigated by furtherexperiments on puncturing the apical cell. When the apical cellgroup is damaged, leaf primordia, which may be orientated abnormally,continue to be formed on the meristem, but one or more budsmay also arise. The observations reported here indicate thata zone at the periphery of the apical meristem is particularlyreactive when the apical cell group is damaged, the majorityof buds being induced in this region. The extent of damage tothe apex may affect the sequence of organogenesis: when damageis extensive buds tend to be formed immediately, subsequentprimordia developing as leaves; when the damage is confinedto the apical cell, or extends to only a few of its segments,bud formation tends to be delayed. It is concluded that the effect of the apical cell on organformation is exercised through the growth and organization ofthe apex as a whole.     

Taxonomy, distribution and nesting biology of species of the genus Dolichovespula (Hymenoptera, Vespidae)

The genus Dolichovespula consists provisionally of 18 species. Aerial nest site characteristics have been established for seven species but most of these species show flexibility in their choice of nest sites and two species often nest in shallow subterranean situations. Colony length is usually just over 3 months to approximately 4 months, but at lower latitudes may extend to more than 5 months. Mature colony size is usually approximately 1000 cells with more large cells than small cells. Parasitized colonies have a shorter colony cycle and smaller colonies. During the production of the sexual brood the larva/worker ratio reaches its lowest value of approximately 2.5 larvae per worker. Colonies often have upper mixed combs of small and large cells. Total adult production is usually less than 2000 adults. Colonies of D. arenaria and D. norwegica may specialize in mainly producing males or queens. Variations in mature colony size and production of queens is probably a consequence of the number of workers present, particularly early in the colony cycle.     

Constant Production of Type C Virus Particles in a Continuous Tissue Culture derived from Pleural Effusion Cells of a Lymphoma Patient

PARTICLES resembling viruses were first observed in organs of mice with spontaneous leukaemia and in thin sections of a biopsy specimen from a lymph node of a patient with acute lymphocytic leukaemia by Dmochowski and Grey¹. They also found them in some biopsy specimens of lymph nodes and bone marrows before and after growth in tissue culture^2,3,8. Recent reports have described the presence of type C virus particles in other human tumours including liposarcoma⁴, osteosarcoma^5,6, giant cell tumour⁹, rhabdomyosarcoma (unpublished results of L. D. and E. S. P.) and breast carcinoma⁷.